Because IgA is very T cell dependent, the T cells regulating IgA are of central importance in secretory immunity. Despite this, very little is known about them. Previous work, which used mitogens, suggested that a separate subset of T cells regulates IgA which is distinct from the subsets which regulate IgG or IgM. New assay systems have been developed with which to study antigen specific T cell regulation of antibody responses after antigen feeding. The specific objectives of this proposal include: 1) to determine the helper and suppressor T cell activity for specifc IgA antibody in lymphoid tissues after antigen feeding, and to compare it to that for IgG and IgM antibody. 2) To define the cellular interactions in gut associated lymphoid tissues (GALT) which occur after antigen feeding includin macrophage-T cell and T cell-T cell interactions. 3) To determine whether substances given orally along with antigen will act as adjuvants for the subsequent mucosal or systemic humoral immune response. 4) To test the hypothesis that a separate subset of T cells regulate IgA responses by cloning antigen specific regulatory T cells from GALT.